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Questions >> JEEMAIN and NEET >> Physics

Physics

In a stationary wave successive nodes and antinodes are separated by 25 cms . If the frequency of a vibrating particles is 250 Hz . The velocity of sound is

asked Mar 7, 2014 by yamini.v

1 answer

Density and youngs modulus of a certain hypothetical material are $\;5 \;gm/cm^{3}\;$ and $\;2\times10^{10} pa\;$ velocity of sound in this material is

asked Mar 7, 2014 by yamini.v

1 answer

At , atmosphere pressure and a certain temperature the velocity of sound is 350 m/s of a certain gas . For the same gas at same temperature the velocity of sound at 2 atm pressure is : (consider ideal gas)

asked Mar 7, 2014 by yamini.v

1 answer

Wavelength of a wave in a certain medium is 20 cm and its velocity is 350 m/s . The same wave is transmitted into a medium where the velocity is 1400 m/s . Its wavelength in the medium would be ?

asked Mar 7, 2014 by yamini.v

1 answer

A longitudinal wave of frequency 1000 Hz is travelling in a medium . At a certain point in the medium there is a compression at certain moment . How many milliseconds later would the next rare faction form at this place ? If the velocity of wave is 350 m/s , how for is the earlier compression at this time ?

asked Mar 7, 2014 by yamini.v

1 answer

A longitudinal wave of frequency 1000 Hz is travelling in a medium . At a certain point in the medium there is a compression at certain moment . How many milliseconds later would the next rare faction form at this place ?

asked Mar 7, 2014 by yamini.v

1 answer

The fast neutrons can easily be slowed down by :

asked Mar 6, 2014 by yamini.v

1 answer

Consider $\;\alpha\;, \beta \;, \gamma\;$ rays each having an energy 1 MeV . Arrange them in increasing order of penetrating powers of radiation.

asked Mar 6, 2014 by yamini.v

1 answer

A Beta decay is a type of radioactive decay in which a beta particle (an electron or a positron) is emitted from an atomic nucleus. During a negative beta decay $\beta^{-}$, which of the following happens?

asked Mar 6, 2014 by yamini.v

1 answer

The binding energy per nucleon of deuteron $\;(_{1}^{2}H)\;$ and helium nucleus $\;(_{2}^{4}He)\;$ is 1.1 MeV and 7 MeV respectively . If two deuteron nuclei react to form a single helium nucleus, the energy released is

asked Mar 6, 2014 by yamini.v

1 answer

If a nucleus disintegrates i two two nuclear parts which have their velocities in ratio 2 : 1 . The ratio of their nuclear sizes will be .

asked Mar 6, 2014 by yamini.v

1 answer

In a sample of radioactive substance what fraction of initial no . of nuclei will remain undecayed after time $\;t=\large\frac{T}{2}\;$ , where T = half - life of substance

asked Mar 6, 2014 by yamini.v

1 answer

At time zero, there are 10.0 grams of W-187. If the half-life is 23.9 hours, how much will be present at the end of seven days?

asked Mar 6, 2014 by yamini.v

1 answer

In a radioactive process nucleus X finally transforms into a stable nucleus Y . Then X & Y can be :

asked Mar 6, 2014 by yamini.v

1 answer

A radioactive nucleus is being produced at a constant rate x per second . If decay constant is K . If $\;N_{0}\;$ are no . of nuclei at time t=0 , then maximum no . of nuclei possible are :

asked Mar 6, 2014 by yamini.v

1 answer

There are two radioactive substances X & Y . If Decay constant of Y is 2 times of X . Initially both have equal number of nuclei . Then after n half lives of X rate of disintegration of both are equal . The value of n is

asked Mar 6, 2014 by yamini.v

1 answer

If activity of a radioactive substance's $\;A_{1}\;$ at time $\;t_{1}\;$ & $\;A_{2}\;$ at time $\;t_{2}\;$ $\;(> t_{1})\;$ . Its decay constant is $\;\lambda\;$ . Then no . of atoms decayed between time $\;t_{1}\;$ & $\;t_{2}\;$ are

asked Mar 6, 2014 by yamini.v

1 answer

A sinusoidal electromagnetic plane wave travels through the empty space in $x$ - direction. The electric wave is polarized in the $y$ - direction frequency of waves is $1.5\: GHz$. At a certain point $P$ in space, the oscillating $E_y$ attains a maximum magnitude $E_o = 6.3 \: m V/m$ \[\] The direction of magnetic field vector is along?

asked Mar 5, 2014 by thanvigandhi_1

1 answer

A sinusoidal electromagnetic plane wave travels through the empty space in $x$ - direction. The electric wave is polarized in the $y$ - direction frequency of waves is $1.5\: GHz$. At a certain point $P$ in space, the oscillating $E_y$ attains a maximum magnitude $E_o = 6.3 \: V/m$ \[\] The direction of magnetic field vector is along?

asked Mar 5, 2014 by thanvigandhi_1

1 answer

A sinusoidal electromagnetic plane wave travels through the empty space in $x$ - direction. The electric wave is polarized in the $y$ - direction frequency of waves is $1.5\: GHz$. At a certain point $P$ in space, the oscillating $E_y$ attains a maximum magnitude $E_o = 6.3 \: mV/m$ \[\] The maximum magnitude $B_o$ of the magnetic field at the point is

asked Mar 5, 2014 by thanvigandhi_1

1 answer

A sinusoidal electromagnetic plane wave travels through the empty space in $x$ - direction. The electric wave is polarized in the $y$ - direction frequency of waves is $1.5\: GHz$. At a certain point $P$ in space, the oscillating $E_y$ attains a maximum magnitude $E_o = 6.3 \: V/m$ \[\] What is the wavelength of the wave?

asked Mar 5, 2014 by thanvigandhi_1

1 answer

According to electromagnetic wave theory, the electric and magnetic field vector associated with the wave is given by \[\] $|E| = E_{max} \cos(kx – \omega t)$ \[\] $|B| = B_{max} \cos(kx – \omega t)$ \[\] The energy of electromagnetic wave is confined in the form of electric and magnetic fields. The energy per unit volume in an electric field is given by $U_E = \large\frac{1}{2} \in_oE^2$ and the energy per unit volume in a magnetic field is given by $ U_M =\large\frac{1}{2} B^2/ \mu_0$ . The energy density associated with the magnetic field is equal to the energy density associated with the electric field. The total energy is equally shared by the electromagnetic as well as magnetic field. The rate of flow of energy in an electromagnetic wave is defined as pointing vector $S = 1/\mu_o (E \times B)$. A plane electromagnetic wave varies sinusoidally at $90\: MHz $ as it travels along the $+ve\: x$ direction. The peak value of the electric field is $2\: millivolt/m$ and it is directed along $ \pm y$ direction \[\] The average energy density in the radiation is

asked Mar 5, 2014 by thanvigandhi_1

1 answer

According to electromagnetic wave theory, the electric and magnetic field vector associated with the wave is given by \[\] $|E| = E_{max} \cos(kx – \omega t)$ \[\] $|B| = B_{max} \cos(kx – \omega t)$ \[\] The energy of electromagnetic wave is confined in the form of electric and magnetic fields. The energy per unit volume in an electric field is given by $U_E = \large\frac{1}{2} \in_oE^2$ and the energy per unit volume in a magnetic field is given by $ U_M =\large\frac{1}{2} B^2/ \mu_0$ . The energy density associated with the magnetic field is equal to the energy density associated with the electric field. The total energy is equally shared by the electromagnetic as well as magnetic field. The rate of flow of energy in an electromagnetic wave is defined as pointing vector $S = 1/\mu_o (E \times B)$. A plane electromagnetic wave varies sinusoidally at $90\: MHz $ as it travels along the $+ve\: x$ direction. The peak value of the electric field is $2\: millivolt/m$ and it is directed along $ \pm y$ direction \[\] The magnetic field vector as a function of time$(t)$ and space$(x)$ is

asked Mar 5, 2014 by thanvigandhi_1

1 answer

According to electromagnetic wave theory, the electric and magnetic field vector associated with the wave is given by \[\] $|E| = E_{max} \cos(kx – \omega t)$ \[\] $|B| = B_{max} \cos(kx – \omega t)$ \[\] The energy of electromagnetic wave is confined in the form of electric and magnetic fields. The energy per unit volume in an electric field is given by $U_E = \large\frac{1}{2} \in_oE^2$ and the energy per unit volume in a magnetic field is given by $ U_M =\large\frac{1}{2} B^2/ \mu_0$ . The energy density associated with the magnetic field is equal to the energy density associated with the electric field. The total energy is equally shared by the electromagnetic as well as magnetic field. The rate of flow of energy in an electromagnetic wave is defined as pointing vector $S = 1/\mu_o (E \times B)$. A plane electromagnetic wave varies sinusoidally at $90\: MHz $ as it travels along the $+ve\: x$ direction. The peak value of the electric field is $2\: millivolt/m$ and it is directed along $ \pm y$ direction \[\] The wavelength and period of the wave is respectively

asked Mar 5, 2014 by thanvigandhi_1

1 answer

S1: The ground waves can bend round the corners of the objects on earth. \[\] S2: The ground wave propagation can be used for very large distance propagation.

asked Mar 5, 2014 by thanvigandhi_1

1 answer

S1: Radio waves can be polarized. \[\] S2: Sound waves in air are longitudinal in nature.

asked Mar 5, 2014 by thanvigandhi_1

1 answer

S1: Shielding is required around high energy particle accelerators and high voltage power supplies in T.V. sets \[\] S2: Every accelerated charge particles radiate electromagnetic radiations

asked Mar 5, 2014 by thanvigandhi_1

1 answer

S1: Electromagnetic waves with frequencies more than the critical frequency of ionosphere cannot be used for communication using sky wave communication. \[\] S2: The refractive index of ionosphere becomes very high for frequencies higher than the critical frequency.

asked Mar 5, 2014 by thanvigandhi_1

1 answer

Calculate the magnetic field between the plates at a point $15\: cm$ from the axis.

asked Mar 5, 2014 by thanvigandhi_1

1 answer

A $30\: pF$ capacitor has circular plates of area $100\: cm^2$. It is charged by a $70\: V$ battery through a $2\Omega$ resistor. At the instant, the battery is disconnected; the electric field between the plates is changing most rapidly. At this instant, find the rate of change of electric field between the plates.

asked Mar 5, 2014 by thanvigandhi_1

1 answer

A parallel plate capacitor as shown in the figure is made of circular plates each of radius $R = 6\: cm$, and it has a capacitance $C = 100\: pF$. The capacitor is connected to a $230\: V$ ac supply with a frequency of 300 rad/s. The amplitude $B$ at a point $3\: cm$ from the axis between the plates is

asked Mar 4, 2014 by thanvigandhi_1

1 answer

Figure shows a capacitor made of two circular plates each of radius $12\: cm$, and separated by $5\: cm$. The capacitor is being charged by an external source. The charging current is constant and equal to $0.15\: A$. The rate of change in potential difference between the plates is

asked Mar 4, 2014 by thanvigandhi_1

1 answer

Calculate the electric field produced by the radiation coming from a $100\: W$ bulb at a distance of $3\: m$. Assume that the efficiency of the bulb is $2.5\ %$ and it is a point source.

asked Mar 4, 2014 by thanvigandhi_1

1 answer

A parallel plate capacitor with circular plates of radius $1\: m$ has a capacitance of $1\: nF$. At $t = 0$, it is connected for charging in series with a resistor $R= 1\: M\omega$ across a $2V$ battery. Calculate the magnetic field at a point $ P$, halfway between the centre and the periphery of the plates, after $t = 10–3s$. (The charge on the capacitor at time $t$ is $q (t) = CV [1 – exp (–t/\tau)]$, where the time constant $\tau$ is equal to $CR$.)

asked Mar 4, 2014 by thanvigandhi_1

1 answer

Electromagnetic waves travel in a medium at a speed of $2 \times 10^8 m/s$. The relative permeability of the medium is $1$. Calculate the relative permittivity.

asked Mar 4, 2014 by thanvigandhi_1

1 answer

A parallel plate capacitor with rectangular plates is being discharged. Consider a rectangular loop centered on the plates and between them. The loop measures a by $2a$, the plate measures $2a$ by $4a$. What fraction of the displacement current (i) is encircled by the loop?

asked Mar 4, 2014 by thanvigandhi_1

1 answer

A parallel plate capacitor with plate area $A$ and separation $d$ between the plates is charged by a constant current $i$. Consider a plane surface of area $ \large\frac{A}{2}$ parallel to the plates and drawn symmetrically between the plates. Find the displacement current through this area.

asked Mar 4, 2014 by thanvigandhi_1

1 answer

Which of the following statements is correct in relation to electromagnetic waves in an isotropic medium? <br> <br> (a) Energy due to electric field is equal to that due to magnetic field. <br> (b) Electric vector E and, magnetic vector B are in phase. <br> (c) For a given amplitude of E vector, the intensity increases as the first power of frequency f <br> (d) For cylindrical wave fronts, the amplitude of the wave varies in proportion to $ \large\frac{1}{r^2}$ , where $r$ is the radius of the wave front.

asked Mar 4, 2014 by thanvigandhi_1

1 answer

S1: In an electromagnetic wave, the average energy density of electric field is equal to the average energy density of the magnetic field \[\] S2: Electric and magnetic fields are related as $E = cB$

asked Mar 3, 2014 by thanvigandhi_1

1 answer

If an electron and a proton having same momentums enter perpendicularly to a magnetic field, then

asked Mar 3, 2014 by thanvigandhi_1

1 answer

The $rms$ value of the electric field of the light coming from the sun is $720\: N/C$. The average total energy density of the electromagnetic wave is

asked Mar 3, 2014 by thanvigandhi_1

1 answer

Given below are some famous numbers associated with electromagnetic radiations in different contexts in physics. Which of the following belongs to radio waves?

asked Mar 3, 2014 by thanvigandhi_1

1 answer

S1: Magnetic flux is vector quantity. \[\] S2: Value of magnetic flux can be positive, negative or zero.

asked Mar 3, 2014 by thanvigandhi_1

1 answer

The variation of current versus time is \[\] The potential difference across a 2H inductor as function of time is shown in figure. At time $t=0$, current is zero.

asked Mar 3, 2014 by thanvigandhi_1

1 answer

Current at $t = 1 \: s$ is

asked Mar 1, 2014 by thanvigandhi_1

1 answer

Area under $V_L - t$ graph gives

asked Mar 1, 2014 by thanvigandhi_1

1 answer

Magnitude of induced emf produced in a coil when a magnet is inserted into it depends on the

asked Mar 1, 2014 by thanvigandhi_1

1 answer

Calculate the energy of electromagnetic waves of wavelength $3000\: A^{\circ}.$

asked Mar 1, 2014 by thanvigandhi_1

1 answer

A plane electromagnetic wave in the visible region is moving along the $z$ direction. The frequency of the wave is $0.5 \times 10^{15}Hz$ and the electric field at any point is varying sinusoidally with time with amplitude of $1\: V/m$. Calculate the average values of densities of the magnetic field.

asked Mar 1, 2014 by thanvigandhi_1

1 answer

Find the average energy stored in a 60 cm length of a laser beam operating at $4\: mW.$

asked Mar 1, 2014 by thanvigandhi_1

1 answer

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